The ultimate objective is to identify environmental causes producing new increases in cancer risk among residents of the area served by the Colorado Regional Cancer Center. The focus will be on increases of previously rare cancers since large relative increases should be visible even with only early (i.e., incomplete) case ascertainment. A computer program will be created to analyze the monthly-updated tape file of the Colorado Central Cancer Registry for increases in cancers of unusual histology or in patient groups in which the cancers had been uncommon. Entities showing a suspicious increase will be selected for two kinds of interview investigation: follow-back on cases already in the Registry files and interviews of new patients as they are admitted to regional hospitals.